In heat source systems such as room cooling and heating, there are technologies for increasing and decreasing the number of operating heat source devices that feed a medium such as chilled water or hot water to air conditioners in accordance with the load demand from the air conditioners (Patent Document 1). In this type of heat source system, in addition to a primary pump that feeds heat transfer medium to the heat source device, frequently a secondary pump is provided between the heat source device and the air conditioner for the purpose of re-pressurizing and feeding the heat transfer medium to air conditioners distant from the heat source device. Also, in the case of such a configuration, normally the heat source device and the secondary pump are controlled independently.
As disclosed in Patent Document 1, the number of heat source devices is determined in accordance with the measured value of the flow rate of the heat transfer medium flowing in a primary pipe (primary pipe flow rate) or the measured value of the load at the air conditioner, for example, on the basis of the demand from the load side. Specifically, when the primary pipe flow rate or the measured load value increases, the number of operating heat source devices is controlled to be increased, and when the primary pipe flow rate or the measured load value decreases, the number of operating units is controlled to be decreased.